<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .active{
            color: aqua;
        }
    </style>

</head>
<body>
<div id="app">
  <ul>
    <li v-for="(item,index) in games"
        :class="{active: currentIndex === index}"
        @click="liClick(index)"
    >{{item}}</li>
  </ul>
</div>

<script src="../js/vue.js"></script>
<script>
    const  app = new Vue({
      el:'#app',
      data:{
        games: ['wow','lol','dota','csgo'],
        currentIndex: 0
      },
      methods: {
        liClick(index) {
            this.currentIndex = index;
        }
      }
    })
</script>
</body>
</html>